Improvement in vitrified knobs



l S.IHILER,v Vtrifived Knob..

'UNrrnD S'rnrns INI PROV'EMENT IN vlTmF-IED AkNolss.

Speciication forming part of Letters Patent No. 197,468, dated November27, 1877; application filed February 20, 1877.

To all whom it may concern:

ne a known that i, sELAn HILER, 0f the city and State of New York, haveinvented an Improvement in the Manufacture of Vitriied Knobs, of whichthe following is a specication:

In the manufacture of door-knobs, pictureknobs, and drawer-knobs it hasbeen usual to provide a recess at the back of the knob for the screw orsocket and the metal that is cast around the same, to hold it in place.

In many instances this recess has been undercut, or made' with someportions of the inner end of the recess largest. This undercutting hasusually been done with atool or gouge while the clay is in the softcondition after molding and before baking. Difculty arises in makingthese recesses perfectly uniform, and the knob is liable to injury whilebeing gouged or undercut.

My invention is made to obviate these difficulties, and relates to themethod of manufacturing said knob, by which the undercut recess isformed by a combustible ring, core, or plug, that is consumed during theprocess of baking or vitrifying, and hence the recess is left in aperfect and uniform shape, corresponding to the combustible core orring.

In the drawing, Figure l is a section of the mold and core for formingthe knob. Fig. 2 is a section of a drawer-knob, with the combustiblering in place. Fig. 3 is an end view of the plug and ring; and Fig. 4 isa section of a door-knob.

The mold is made of the cylinder a, lifter b, and plunger c, andtwo-part ring d, as usual in the manufacture of drawerknobs; but in themanufacture of door-knobs this two-part ring d is not required.

From the lifter or bottom plunger d there extends the plug or core e,and there is a supplemental lifter, j', upon the lifter b, with a stiffspring, h, between them, and the extent to which the spring can becompressed is limited by a suitable stop, 3, on the lifter.

The object of this is to cause the plug or core e to be partiallywithdrawn before the pressure is relieved from the knob, because if thisis not done the clay is liable to be broken around the plug. Inconsequence of the spring being compressed as the clay is squeezed inthe mold, the knob will be properly molded 5 but as the pressure isliberated the spring raises the supplemental lifter and knob, or drawsthe core or plug e partly back, so as to loosen it from the claysuiiciently to allow its `complete separation as the mold opens withoutinjury to the knob.

This core may be vcylindrical or prismatic. I have shown it with afeather, 6, at one side to form a groove that prevents the shank orsocket turning.

The conical ring of wood e' is placed upon a stud at the end of the plugor core c, and its exterior is of the size and shape required to formthe undercut of the recess. One of these rings is put upon the plug orcore before the knob is pressed,and when the plug withdraws from theknob the ring is left in the knob, and it is burnt out in the process ofvitrifying or baking.

It will be evident that other combustible material than wood may beused, and that the whole plug or core may be of combustible material, oronly the separate ring.

In molding door-knobs in the aforesaid manner I am enabled to withdrawthe core from the thin shank Z, (shown in Fig. 4,) so as to make lthehandle and vitrified shank in one piece, "but it is usually best to haveseparate pieces, sitting together, as shown at the line 5, and these areunited by a luting of clay before the knob is vitrifled. This mineralshank is thin and hollow, 'and corresponds generally to the shape of themetal shanks heretofore employed on door-knobs, and the hollow porcelainshank receives the metal socket for the lock-spindle, so that theporcelain shank covers up the said socket, and improves the appearanceofthe knob.

lt is to be understood that the metal shank of the door-knob is fastenedinto the undercut portion of the knob, either directly orintermediately, by a thin metal tube that sur'- rounds the spindle. Thisis done to prevent strain upon the thin hollow vitriied shank, and thespace between this vitriiied shank and the spindle may be iilled in withplaster or other suitable material.

I claim as my inventionl. The method herein specified of moldingrecessed knobs, by-leaving in the clay a combustible plug, core, orring, and burning theI fled, the knob portion having an undercut refsame out in vitrifying the knob, substantially y cess for receiving theinner end of the metal as set forth. spindle socket, substantially asset forth.

2. The combination, with the knob-mold, Signed by me this 15th day ofFebruary, lifter, and plunger, of the auxiliary follower A. D. 1877.

or lifter f, spring h, and plug or core e, sub- S. HILER. I stantiallyas and for the purposes set forth. Witnesses:

3. The mineral door-knob, made of the hol- GEO. T. PINGKNEY,

lor shank and knob portions united7 as speoi- GHAs. H. SMITH.

